[libunwind] [libunwind][cmake] Compile _Unwind* routines with -fexceptions (PR #121819)

[Alex Rønne Petersen via cfe-commits]

alexrp wrote:

> > I wonder if it would be less bug-prone in the long term to just build the whole library with `-fexceptions` instead of trying to apply `-fexceptions` to _just_ the right files at this point in time. Feels like a brittle optimization for not much gain?
> 
> This will break MinGW LTO libunwind.

Can you clarify how?

https://github.com/llvm/llvm-project/pull/121819